Staphylococcus aureus is responsible for a variety of human infections and as routinely isolated is not encapsulated. In recent years a number of encapsulated stephylococci have been recovered from clinical specimens. Such organisms are virulent for mice by virtue of the antiphagocytic properties of their capsules. The objective of the proposed research is to rigorously characterize several staphylococcal capsular polysaccharides chemically and biologically, and to explore the relationship of these encapsulated strains to staphylococcal disease. Chemically, the compounds found thus far in staphylococcal capsules include aminoglucuronic acid, aminomannuronic acid, aminogalacturonic acid, fucosamine, L-alanine and taurine. Immunologically, the compositions are reflected in several antigenic types. From partial acid hydrolysates, oligosaccharides will be isolated and characterized by combined gas liquid chromatography-mass spectrometry and nuclear magnetic resonance spectrometry. Immunological determinants will be identified in the structure of the polysaccharides deduced from the fragmentation studies. As multiply antibiotic resistant staphylococci become ever more of a problem in hospital environments, the need for alternate means of therapy becomes ever more pressing. Multivalent vaccines for meningococci and pneumococci, based on their capsular polysaccharides, have been licensed for selective use in the United States. A long range practical objective of the proposed research is not only improving means of detecting staphylococci and predicting their pathogenicity, but also exploring the potential of a staphylococci vaccine for selected use based on polysaccharide capsular antigens.